Two essential components of the Projects of this Program will be supported by this Core. The first is the characterization of novel or modified peptides and proteins by Edman based chemical sequencing and mass spectrometric techniques. The second is the expression and purification of proteins that are required by the Projects for biological and biochemical investigations. Protein characterization is an essential part of this Program. The Core provides both state-of-the-art instrumentation and highly trained investigators and support personnel to carry out these characterizations. The Core will characterize novel peptides, proteins or post-translational modifications of known proteins being studied by Program investigators and in particular, mediators involved in actin and inhibin signaling. In addition, we will confirm the sequence and post-translational modifications of recombinant proteins that the Projects generate for use in biological and crystallization studies. Several projects require large quantities of proteins such as activin, activin mutants, inhibin, and soluble fragments of receptors. The Core will generate these proteins by expressing the genes in a suitable system (e.g. baculovirus/insect, mammalian, or yeast cells). The proteins will be purified and characterized using appropriate discriminatory analytical techniques.